4 Answers
4

Take breaks. No chair is comfortable for 8-11 hours. We used to do frisbee after big fights. Now it's hacky sack. It doesn't have to be a long break, just enough to get the blood flowing in your legs again.

Look at how to sit at a table. There are plenty of postures that will reduce fatigue and save your back from injuries. A towel on the back of your lombar region helps you maintain a good posture.

Exercise balls are a good source as well and $wife may have one you can borrow. Again, you will need to learn how to sit on it but the additional bonus is that you can get exercise while doing RPG.

I would look at camping chairs like the outwell comfort chair or anything like that. Go to a out doors shop and try them. There are plenty of models, they tend to be cheap, and some are quiet confiortable. The added bonus is that you can use it in your next garden party!

I find that I stand at the table for most of the session. You have to be careful not to get into other people's space, and not to 'hover' over the map.. but getting up and walking around, helps me for long sessions.